A friend fabbed up some 92" long ramps for my 16' car hauler. They slide under the dove tail sideways nicely (he also did some brackets).

They work very well on my lowered Turbo Look (deep front spoiler), although I still need to jack up the front of the trailer about 4".

A word of caution though, my ramps are steel and quite heavy. Aluminum would be much better.

Also, sideways mounted means you need to have room on the side to slide them in and out. If someone parks next to you and leaves, you need to move the trailer to get the ramps back in. Not amusing after a long hot day at an event.

There is a picture somewhere (here or maybe Corner-Carvers.com) of a set of fabbed up folding ramps that attach to the end of the trailer with piano-type hinges. Pretty nifty.

I had an 18' "Big Tex" trailer that had the integral slots to stow the ramps. I needed 11' ramps to get my car up without having to resort to secondary extensions. I've always hated secondary extensions as they are one more thing to have to set-up, take with, or cause a problem.